This project explores the effects of polycyclic aromatic hydrocarbons (PAHs) on development in an ecological context. The project will include studies of a population of killifish (Fundulus heteroclitus) inhabiting a highly PAH-polluted estuary in Virginia, the Elizabeth River (ER), that includes a Superfund site. This population is highly resistant to the developmental impacts of PAHs occurring at this site and to laboratory exposures to specific PAHs, relative to killifish from uncontaminated sites. Thus the Elizabeth River phenotype provides an opportunity for studying evolutionary impacts of pollution, including mechanisms of adaptation and consequences of adaptation. And importantly, understanding mechanisms of adaptation will provide insight into mechanisms of developmental toxicity of PAHs, now becoming recognized as a critical target of this increasingly prevalent class of Superfund chemicals for both wildlife and human health. Other studies with killifish from a reference site and with zebrafish will explore specific mechanisms of PAH developmental toxicity, including effects on mitochondrial function and mtDNA damage, and the consequences of low level PAH exposures in embryos for later life stages. Consequences will include explorations of tissue architecture, effects of later life exposures to other Center chemicals, and in collaboration with other Center projects and cores, neurobehavioral effects will be emphasized. The specific aims of the project are: 1. To determine the mechanisms underlying resistance to PAH-mediated embryotoxicity in the Elizabeth River population of killifish. 2. To determine positive or negative consequences of this resistant phenotype. 3. To determine the effects of PAHs and other chemicals of interest to the Center on mitochondrial DNA and mitochondrial function during embryonic development. 4. To determine the later life consequences of low level PAH exposures to embryos. These aims will be accomplished through a highly collaborative effort among a molecular toxicologist (Dr. Joel Meyer), a fish pathologist and ecotoxicologist (Dr. David Hinton) and an aquatic biochemical toxicologist (Dr. Richard Di Giulio).